1. Field of the Invention
The present invention relates to a charging member and to a process cartridge or the like using the charging member.
2. Description of the Related Art
In an electrophotographic apparatus adopting a contact charging mode, toner, an external additive used in the toner, a discharge product, a paper powder, or the like may adhere to the surface of a charging member, which is brought into contact with an electrophotographic photosensitive member, owing to long-term use of the apparatus.
For example, the electrophotographic apparatus is provided with a cleaning blade for removing the toner remaining on the surface of the electrophotographic photosensitive member even after the step of transferring a toner image. In recent years, however, reduction in the particle diameter of the toner and its spheroidization have progressed, and hence it has started to become easy for the toner to escape the cleaning blade. The toner that has escaped the cleaning blade moves toward the surface of the charging member at a nip between the electrophotographic photosensitive member and the charging member, and in the end, fixes onto the surface of the charging member in some cases. In the charging member having on its surface a portion onto which the toner has fixed, the portion may differ from any other portion in ability to charge the electrophotographic photosensitive member, and the difference serves as an obstacle to uniform charging of the electrophotographic photosensitive member in some cases.
In addition, when image formation is intermittently performed with the electrophotographic apparatus, the rotation of the electrophotographic photosensitive member may stop once. In this case, such state that the toner accumulates on the portion of the electrophotographic photosensitive member abutting on the cleaning blade is established. In addition, when the electrophotographic photosensitive member starts to rotate again thereafter, the toner accumulating on the portion of the electrophotographic photosensitive member abutting on the cleaning blade escapes the cleaning blade to adhere to the surface of the charging roller in a streak fashion in some cases. An electrophotographic image formed by the electrophotographic photosensitive member charged by the charging member to which the toner has adhered in a streak fashion may show streak-like unevenness corresponding to the streak-like toner adhering to the charging member.
With regard to the adhesion of the toner that causes such problem, Japanese Patent Application Laid-Open No. 2002-080785 discloses a conductive, organic-inorganic hybrid film that is formed of a metallic alkoxide and/or a metalloid alkoxide formed by a sol-gel method, and an organosilicon compound, and disperses conductive filler therein. In addition, Japanese Patent Application Laid-Open No. 2002-080785 describes that the organic-inorganic hybrid film is excellent in toner releasability because of its large contact angle with water.
As a result of investigations conducted by the inventors of the present invention on the invention according to Japanese Patent Application Laid-Open No. 2002-080785, however, the inventors have acknowledged that an additional reduction in the surface free energy of the surface of the charging member needs to be achieved for suppressing the streak-like adhesion of the toner to the charging member upon such intermittent electrophotographic image formation as described above.